It is well known that operators of agricultural tractors, either because of lack of knowledge or lack of care, frequently abuse the power take-off (PTO) clutches by engaging the PTO clutch when the tractor engine is running at too high a speed or by engaging the PTO clutch with a stalled output receiving the rotational power from the PTO. This has necessitated the design of clutches with heat-dissipating capacity greater than that required for normal or non-abusive use.
Schott et al U.S. Pat. No. 4,938,302 discloses a mechanical interlock device for preventing PTO clutch engagement when the engine speed is excessive, thereby permitting the use of PTO clutches having reduced heat-dissipating capacity. While the patented device works quite well and serves its intended purpose, it is a mechanical device which may be defeated by an operator. An electrical interlock would be less costly, require less maintenance, and be more difficult to defeat.